The present invention relates to machines for forming, filling and sealing packages which are made from an elongated thin flat sheet of flexible packaging material. In general, the sheet of flexible packaging material is formed by the apparatus into a vertically depending, upwardly open tube having overlapping longitudinal edges. Thereafter, the overlapping edges are longitudinally sealed together by means well known to those in the art and the end of the tube is sealed together by a pair of transverse heat seals which are vertically spaces apart. At this point the tube is filled from above with a measured quantity of product. A second heat sealing operation, which is performed after the filled tube has been downwardly advanced, completes enclosure of the product. Simultaneously with or shortly after the transverse heat sealing step the tube is completely transversely severed by known cutting means in the space between the vertically spaced apart pair of transverse heat seals. Thereafter the tube is downwardly advanced and the cycle is successively repeated so as to form a multiplicity of individually packaged products.
Many means for advancing the vertically depending, upwardly open tube downwardly over the mandrel are conventional in the art. For example, as stated above, it has been conventional practice to employ heat sealing means for closing (e.g. sealing) the tube by forming a pair of vertically spaced apart transverse heat seals. In one conventional embodiment the sealing bars are moveable in both the horizontal and vertical planes. That is, the sealing bars are intermittently moved horizontally inwardly to engage and compress the tube and form a pair of vertically spaced apart transverse heat seals and are then moved vertically downwardly to feed or draw the packaging material over and past the tube forming mandrel. The transverse heat sealing of the tube occurs during this operation. Thereafter, the sealing bars move horizontally outward to release the tube and return vertically to their starting position.
A further conventional practice in advancing or feeding the packaging material over the mandrel involves the use of a vacuum belt mechanism. In this apparatus a pair of perforate endless belts are disposed respectively on opposite sides of the tube to engage and feed the tube downwardly as a result of a reduced pressure or vacuum condition at the openings in the belt. The tube closing or transverse heat sealing means in this arrangement may be stationary vertically but reciprocally moveable horizontally to intermittently engage and transversely heat seal the tube between feed and product drop or fill operations.
Yet another conventional practice for advancing or feeding the packaging material over the tube former or mandrel involves the use of pinch rollers rather than a belt mechanism. In this configuration two rollers are disposed respectively on opposite sides of the tube with the rollers engaging and feeding the tube downwardly over the mandrel as a result of the fact that the tube is pinchingly engaged between the rollers and the outer surface of the mandrel
In all of the foregoing arrangements a relatively long "product drop" is encountered. This product drop is encountered as a result of the fact that the articles to be packaged must be introduced into the interior of the forming mandrel near the top thereof. This arrangement, of course, is necessary since the sheet of flexible packaging material is completely formed into a vertically depending tube shortly below the upper surface of the forming mandrel and access into the interior thereof cannot be gained below this point without destruction of the tubular configuration. Accordingly, the distance which the articles to be packaged must fall upon entrance into the interior of the tube forming mandrel and discharge therefrom is substantial. Additionally, with the vertically moveable transverse heat sealing arrangement the necessary vertical travel of the sealing bars results in a substantial further vertical distance through which an aricle must fall in the filling operation. Furthermore, it should be noted that in this configuration the portion of the formed tube immediately above the tube closing transverse sealing bars is in tension and drawn into a relative sharp or tight "V" configuration during the downward movement of the sealing bars. This configuration is not conducive to a good filling operation nor is the resulting stress at the sealing bars conducive to good sealing.
In the vacuum belt or pinch roller arrangement, the belts or rollers and sealing bar movements can be coordinated to provide for a relaxed condition of the tube above the sealing bars and a relatively shallow or a loose "V" configuration with a slight bulge or ballooning effect can be arrived at. Such a configuration is more conducive to a good filling operation. Transverse heat sealing may also efficiently be accomplished in the absence of stress. The operative run distance of the vacuum belts in that configuration, however, extend through a substantial vertical distance and a relative long product drop distance is, once again, encountered.
While a relatively long "product drop" may not be totally undesirable or unacceptable with articles which are of fairly light weight, it is completely unacceptable when attempting to package articles which are relatively heavy. In particular, a major problem which has developed in attempting to package relatively heavy articles such as, for example, grapefruits, melons, oranges and the like is that the articles, when introduced into the interior of the forming mandrel fall, under the influence of gravity, and impact the preformed transverse heat seals which are utilized to close the tube such that the transverse heat seals are ruptured. Of course, such a situation is wholly unacceptable. This problem exists even when those of skill in the art have attempted to individually package heavy articles.
Accordingly, those of skill in the art have undertaken a quest to provide a vertical form, fill and seal apparatus which will individually package relatively heavy articles without rupturing the transverse heat seals which close the tube as has been present in the past attempts to package such heavy articles. The present inventive apparatus and method provide a satisfactory and cost efficient solution to this outstanding problem.